[The histological, histochemical and ultrastructural characteristics of induced ectopic chondrogenesis].

Implantation of the chondrogenesis inductor (demineralized osseous powder) into the subcutaneous fat in the area of the rat lower extremity muscles caused clear histological, histochemical and ultrastructural manifestations of ectopic chondrogenesis in certain zones of close contact with the inductor. Fibrogenic mesenchyme cells and fibroblasts proliferating by the glottis between the 6 th postoperative day and forming the bands, invading the glottis between the inductor granules were probably the object of chondrogenic transformation. Stages of these cells chondrogenic differentiation, hyaline cartilage forming and manifestations of its following ossification were followed up.

[Effect of single-stranded breaks on the ultrastructural organization and cytochemistry of the chromatin in tumor cells].

Single-stranded DNA breaks in Zajdela's ascitic hepatoma and transformed hamster fibroblasts were caused by treating alive cells with 1% dimethylsulfoxide for 2 h or 100 micrograms/ml bleomycin for 5 min and tested by alkaline and neutral DNA elutions. Electron microscopy of thin sections revealed decompaction of the loosened approximately 25 nm globules within diffuse chromatin into thin fibrillar mesh while supranucleosomal structure of the compact chromatin remained untouched. The chromatin enhanced its affinity for cationic dyes and contrast agents.

[Peculiarities of nicotinic acid formation in coronary heart disease with special reference to heart arrhythmias].

The present work is divided into two parts: clinical observations and experimental investigations. The endogenic formation of nicotinic acid was decreased in all patients with ischaemic heart disease, and we have found an increased accumulation of kynurenine in blood serum after tryptophan loading in many cases - a clear indication of pyridoxal-5-phosphate (P-5-P) deficiency in the organism. The results of experimental investigations showed that L-kynurenine sulphate initiates cardiac dysrhythmias as well as dystrophic changes in cardiomyocytes.

[Conformational changes in the chromatin of tumor cells and the phenomenon of nuclear achromasia].

Tumour cell nuclei display achromasia in smears relative to methylene blue and to other low-affinitive ionic dyes. In the course of the smear air-drying the tumour DNA undergoes conformational changes as evidenced by enhanced ethidium and monomer acridine orange uptake and increased sensitivity to DNAse I hydrolysis. Very mild treatment with bleomycin prevents nuclear achromasia with methylene blue in tumour cells.

Structural changes induced by heparin in Zajdela ascites hepatoma cells.

By method of light and electron microscopy the influence of heparin (0.1%) sodium heparinate) on Zajdela ascites hepatoma cells was studied. To provide penetration of heparin into cells, the latter were treated with low-concentration detergent--Triton X-100.

Ultrastructural study of chromatin fibrils in thin sections of isolated nuclei.

In ultrathin sections of isolated rat liver nuclei and chromatin fibril represents a chain of 250-A globules. Electron microscopic examination of the physiologically loose globules of diffuse chromatin or globules of compact chromatin loosened by heparin treatment has revealed that each 250-A globule contains a nucleosome covered with 60--85-A thick layer -- "a capsule of a nucleosome". Some filaments, approximately 20 A in diameter, can be distinguished within the capsule each being attached to the nucleosome by a dark granule.

[Method of contrast enhancement of DNA-containing structures on ultrathin sections].

Thin epoxy sections of formaldehyde-fixed tissue underwent depurinizing hydrolysis with 5N HCl at room temperature for 1 hour, the treatment with an aldehyde blocking agent, 10% sodium bisulfite, at 60 degrees C during 90 min, and staining with 2% aqueous uranyl acetate. Introduction of bisulfite considerably enhanced the contrast of chromatin. Staining of DNA in these conditions is summed up of preferential binding of uranyl cations with phosphates of DNA and with bisulfite anions specifically bound to deoxyribose.

[Electron-cytochemical method of DNA detection with the aid of ammonia silver].

Three prescriptions for the detection of aldehyde groups of deoxyribose with ammoniac silver are proposed. The reaction can be carried out on tissue blocks or imprints; it is useful for DNA identification in the light and electron microscope, gives high contrast and allows to reveal DNA in structures with a relatively low content of DNA, for instance, in nucleoi. The disadvantages of the method include a possibility of nonspecific reduction of silver if the reaction is performed on a plastic-embedded material and damage of ultrastructures if the reaction is done prior to embedding.

[Differences in the ultrastructure of the subunits of compact and diffuse chromatin].

The ultrastructure of subunits of the compact and diffuse chromatin of isolated Wistar rat hepatocytes nuclei was studied. The complexity of the chromatin subunits composed of the centrally situated nucleosome and of its capsule was confirmed. It was found that the capsule could exist in either compact or diffuse form, thus determining whether the chromatin was compact or diffuse.